Jan. 17, 1916 
Plenodomus fuscomaculans 
747 
founcj in the highly soluble sugars. Such growth forms have commonly 
been recognized as a reaction to high osmotic pressure. Temetz (1900) 
has obtained these in acid solutions. But such growth forms have oc¬ 
curred with this fungus in distilled water and on filter paper, and no 
doubt this growth form, instead of being a specific reaction to concen¬ 
tration, is one induced by a number of unfavorable conditions. 
The action of sorbose has been disregarded, because this sugar is broken 
down by heat. The failure to obtain growth with lactose and erythrose 
is not without parallel in the literature. The action of wheat starch is 
peculiar, in view of the previous successful use of potato starch (Table X). 
The action of lichenin is of great interest. This carbohydrate is a 
dextrin-like compound, almost insoluble in cold water and forming a 
gummy mass in hot water. In the turbid solution of this chemical the 
fungus produced a great number of secondary spores, evidently hypho- 
mycetous. These spores were of^ approximately the same size and 
shape as the ordinary spores of this fungus. The exact method of their 
production was not determined. Mounts of material gave only straight 
mycelial threads and great numbers of detached spores. Dilution plates 
poured from the culture dishes teeming with these spores gave no other 
organism than the one under investigation. The colonies appeared in 
the plates in such abundance as to leave no doubt concerning the relation 
of these colonies to the secondary spores. 
The experiments with carbohydrates may now be summarized. 
Nearly all carbohydrates tried served as a source for carbon. The general 
effect of adding sugars even in so low a concentration as M/50 was to 
stimulate vegetative growth greatly, but this stimulated growth was 
accompanied by a pronounced repression of pycnidium formation. In an 
experiment with M/20 solutions a strong mycelial growth was obtained, 
accompanied by oidia-like bodies, but fructification was absent. With 
slightly soluble carbohydrates, in which the actual amount of available 
soluble material was always limited, vegetative growth was weaker and 
pycnidium production was a general rule. A comparison of these highly 
soluble and slightly soluble carbohydrates indicates that the differences 
in growth form are connected with the amount of food supply rather 
than with the specific nature of the sugar. This position is reinforced 
when we consider that the hydrolysis of inulin, gum arabic, etc., yields 
exactly those sugars which, when tested in M/20 concentration, gave no 
pycnidia. In view of this comparison the earlier conclusion of Roux and 
Linossier (1890) seems untenable, and a more plausible explanation of 
the differences of growth form obtained seems to be found in the con¬ 
centration relations. 
This matter of carbohydrate supply has obviously a marked influence 
upon the problem of the organic media for laboratory use. 
